In recent years, it has become common practice that a camera is incorporated in a personal computer or game console for capturing images of a user for use in a variety of forms. For example, some technologies that are commercially available today such as TV phone and video chat are designed to transmit user's images to other end in an “as-is” manner. Other technologies recognize user's motions by image analysis and use such motions as input information for games and information processing (refer, for example, to PTL 1).
Further, it has become possible in recent years to provide a better sense of realism and image representation by detecting user's motions in a three-dimensional space including a depth direction with high accuracy. Among commercially available techniques adapted for detecting a position of a target in the depth direction are those using parallax between left and right images shot by a stereo camera and others adapted to analyze a reflection time of an emitted infrared beam or an infrared image.